Peel and cut the potatoes into ¼ by ¼-inch thick fries. Place in a large bowl of cold water.
Heat 2 inches of oil in a large, straight-sided pan or deep fryer to 325ºF. Drain the fries in batches on paper towels.
Fry each batch for 3 to 4 minutes until pale blonde and remove to a baking sheet lined with paper towels.
Just before serving, increase the heat of the oil to 375ºF and fry the potatoes again, in batches, until golden brown. Remove to a sheet pan lined with paper towels and season with kosher salt.
FRIED HALIBUT
Preheat the oven to 200°F.
Heat at least 2 inches of oil to 360ºF in a large skillet.
In a shallow dish or pie plate, whisk together the flour, 1 teaspoon salt, and ½ teaspoon pepper. Dredge each piece of halibut in flour, shake off excess, then dip in the eggs, and finally coat evenly with panko.
Fry the fish batches until golden brown on both sides. Remove with a slotted spoon to a paper towel-lined plate. Transfer to a baking sheet and keep warm in the oven.